Treatment of saturated distillates



United States Patent 2,694,034 TREATMENT OF SATURATED DISTILLATES Francis C. Moriarty, Birmingham, Mich., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application June 30, 1950, Serial No. 171,530

11 Claims. (Cl. 196-29) This invention relates to the treatment of saturated distillates and more particularly to a novel method of reduciliilglg the mercaptan content of saturatedhydrocarbon dist ates.

Saturated distillates contain mercaptans which are undesirable for various reasons including objectionable odors, corrosive effect, etc. Conventional methods of reducing the mercaptan content of the distillates include sulfuric acid treatment and caustic treatment, the caustic in many cases utilized with a solutizersuch as methanol, phenols, cresylic acids, etc. The sulfuric acid treatment is generally to be avoided where possible because it is expensive and also results in excessive treating losses. Therefore, this treatment is utilized only in extreme cases where other methods are not satisfactory. The caustic treatment becomes prohibitively expensive when it is utilized to effect substantially complete reduction of the mercaptan content of the distillate. The present invention offers a novel method of reducing the mercaptan content of saturated distillates. This method is also particularly useful in connection with a caustic treatment which is limited to partial reduction of the mercaptans and the features of the present invention are utilized to effect a further reduction of the mercaptans.

While the present invention is particularly applicable to the treatment of saturated gasolines, such as straight run gasoline, natural gasoline, etc., it also may be utilized for the treatment of other light hydrocarbon distillates including naphtha, kerosene, light gas oil, etc. It is understood, that in some cases, it may be necessary to slightly modify the specific details of the present process, depending upon the particular saturated distillate being treated and the mercaptan content thereof.

In one embodiment the present invention relates to a method of reducing the mercaptan content of a saturated distillate which comprises commingling therewith an unsaturated compound and a phenylene diamine type inhibitor.

in a specific embodiment the present invention relates I to a method of reducing the mercaptan content of straight run gasoline which comprises storing said gasoline in the presence of not more than about by weight of an added olefin and from about 0.0001% to about 0.1% of N,N-di-sec-butyl-p-phenylene diamine.

As hereinbefore set forth, the saturated distillate may be reduced in mercaptan content by the addition of an unsaturated compound and a phenylene diamine type inhibitor. It has been found and will be shown in the following examples that the addition of the inhibitor to the saturated distillate, in the absence of the unsaturated compound, does not effect the desired reduction in mercaptan content. Similarly, the addition of the unsaturated compound without the inhibitor also does not effect desired reduction in mercaptan content. Therefore, it is essential that both the unsaturated compound and the inhibitor be present to obtain the desired improvement.

Any suitable unsaturated compound may be utilized in accordance with the present invention. In one embodiment, the unsaturated compound may comprise a mixture of olefins, and when the saturated distillate to be treated comprises a. saturated gasoline, the mixture of olefins advantageously comprises cracked gasoline, polymer gasoline, etc. In another embodiment of the invention, the unsaturated compound may comprise a particular type of olefin, such as: l) Diolefins including allene, butadiene, isoprene, methylisoprene, pentadiene, methylpentadiene,

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etc.; (2) a branch-chain olefin which generally will contain from about 4 to about 12 carbon atoms per molecule and includes such olefins as isobutene, isopentene, isohexene, isoheptene, isooctene, isononene, isodecene, isoundodecene, isododecene, 2,2-dimethyl propene, 2,2-dimethyl butene, 2,2 dimethyl pentene, 2,2 dimethyl hexene, etc., 3,3 dimethyl pentene, 3,3 dimethyl hexene, 3,3 dimethyl heptene, 3,3 dimethyl octene, etc., 2,3 dimethyl-butene, 2,3 -dimethyl pentene, 2,3- dimethyl hexene, 2,3 dimethyl pentene, 2,3 dimethyloctene, etc., 2,2,3-trimethylbutene, 2,2,3-trimethylpentene, 2,2,3 trimethylhexene, 2,2,3 trimethylheptene, 2,2,3- trimethyloctene, etc., 2,2,3,3-tetramethylbntene, 2,2,3,3- tetramethylpentene, 2,2,3,3-tetramethylhexene, 2,2,3,3- tetramethylheptene, 2,2,3,3-tetramethyloctene, etc.; (3) a straight-chain olefin which generally will contain from about 4 to about 12 carbon atoms and includes such compounds as butene-l, butene-2, pentene-l, pentene-Z, hexene-l, hexene-2, hexene-3, heptene-l, heptene-2, heptene-3, octene-l, octene-2, octene-3, octene-4, etc.; (4) a cycloolefin including cyclohexene and alkyl derivatives thereof such as methylcyclohexene, ethylcyclohexene, propylcyclohexene, etc., polymethylcyclohexenes, polyethylcyclohexene, polypropylcyclohexenes, cyclohexadiene, similarly substituted cyclohexadienes, etc. (5) an unsaturated alkyl aromatic compound such as styrene, allylbenzene, phenylbutadiene, phenylacetylene, etc.; (6) unsaturated hydrocarbon compounds containing two or more rings per molecule including such compounds as indene, 1,4-dihydronaphthalene, etc.; and (7) mixtures of the unsaturated compounds herein set forth.

The unsaturated compounds will be used in an amount of not more than about 10% by weight of the unsaturated distillate and more particularly will be within the range of from about 1% to about 10% by weight thereof.

The phenylene diamine type inhibitor preferably comprises N,N'- di sec-butyl p phenylene diamine. Other phenylene diamine type inhibitors comprise N,N'-di-alkylp-phenylene diamines in which the alkyl groups contain from 1 to about 12 carbon atoms per molecule and also includes compounds in which the alkyl groups comprise different alkyl groups such as, for example, in compounds as N-propyl-N-butyl-p-phenylene diamine, N-butyl-N- amyl-p-phenylene diamine, N-hexyl-N'-octyl-p-phenylene diamine, etc.

The concentration of p-phenylene diamine type inhibitor to be added will vary with the particular distillate being treated, with the amount and type of unsaturated compound utilized and with the concentration of the mercaptans in the distillate. In general, the amount of inhibitor will be from about 0.000l% to about 0.1% by weight or more of the saturated distillate. The unsaturated compound and the inhibitor may be added to the saturated distillate in any suitable manner and this includes first adding the olefin and then adding the inhibitor, or vice versa, as well as commingling the inhibitor with the olefin and adding the mixture to the saturated distillate.

As hereinbefore set forth, the novel features of the present invention are particularly advantageous for use in a process in which the saturated distillate is first treated with caustic or otherwise to partially reduce the mercaptan content and then the gasoline is treated with the unsaturated compound and inhibitor to effect further reduction of the mercaptan content. A particularly suitable method for effecting the process of the present invention is to add the unsaturated compound and the inhibitor to the saturated distillate either before or shortly after the same is pumped to the field storage tank. While in the storage tank, the unsaturated compound and inhibitor will serve to effect the reduction of the mercaptans in the distillate. Air inherently will be dissolved in the distillate, either during the pumping and/ or while in the storage tank. It is believed that the air enters into the reaction of the inhibitor and olefin in reducing the mercaptan content of the distillate. Usually sufficient air will be dissolved in the distillate in this manner. However, if for any reason there is a deficiency of air for this purpose, it is within the scope of the invention to add air, oxygen, etc. to the distillate by any suitable well-known means.

The following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

EXAMPLE I The saturated distillate used in this example was a sour West Texas straight run gasoline having an A. P. I. gravity of 608 and a boiling range of from 112 to 384 F. This gasoline had a mercaptan sulfur content of 0.066% by weight. The gasoline was subjected to caustic washing with 10% by volume of 20 Baum caustic to reduce the mercaptan content to 0.039% by weight. However, in order to maintain the mercaptan content of the various samples at a constant value, another portion of the original gasoline was doctor sweetened, and blends were made of the caustic treated gasoline with the doctor sweetened gasoline so that the blends had a mercaptan sulfur conof the inhibitor. The mercaptan content was 0.0055 by weight after 9 days in storage. dentally destroyed after this determination and therefore the value after 14 days was not obtained.

EXAMPLE VI This example shows the effect of different concentrations of the unsaturated compound. In view of the exceptionally good results obtained when using methylpentadiene as the unsaturated compound, methylpentadiene was selected for this series of tests. The blends used contained 40% by volume of the caustic treated gasoline, 60, 59, and 55% by volume of the doctor sweetened gasoline, together with 0, 1, 2, and 5% by volume of methylpentadiene respectively, and or 0.01% by weight of the inhibitor. These tests were continued for 9 days and the results are shown in the following table.

Table I MERCAPTAN SULFUR, WEIGHT PERCENT Inhibitor, Wt. Percent 0 0. 01 0 0. 01 0 0. 01 O 0. 01 Methylpentadiene, Volume Percent 0 1 1 2 2 5 5 Time:

At start 0. 0141 0. 0141 0. 0141 0. 0141 0 0141 0. 0141 0. 0141 0. 0141 After 1 day 0. 0141 0. 0132 0. 0141 0. 0124 0 0124 0. 0113 0. 0124 0. 0111 After 2 days. 0. 0141 0. 0129 0. 0128 0. 0124 0. 0124 0. 0098 0. 0107 0. 0090 After 5 days 0. 0141 0. 0124 0. 0095 0. 0090 0. 0105 0. 0069 0. 0090 0. 0056 After 9 days 0. 0132 0. 0111 0. 0066 0. 0047 0. 0071 0. 0043 0. 0060 0. 0038 tent of about 0.0154%. The samples were stored in the dark at room temperature in vented bottles containing aqueous hydroxide solution, and the mercaptan contents were determined by potentiometric titration methods.

A blend of 40% of the caustic washed gasoline and 60% of the doctor sweetened gasoline had an initial mercaptan content of 0.0154%, which after 14 days in storage was 0.0132%. Upon the addition of 0.01% by weight of N,N'-di-sec-butyl-p-phenylene diamine to another sample of the same blend, the mercaptan content after 14 days was 0.01 15% by weight. While this comprises a reduction in the mercaptan content below that obtained in the absence of the inhibitor, the mercaptan content after 14 days was still too high. In contrast to the above results, another blend of 36% of the caustic treated gasoline and 54% of the doctor treated gasoline with 10% of methylpentadiene and 0.01% by weight of the inhibitor, the mercaptan content after 14 days was reduced to 0.0004% by weight. This last sample is sweet and therefore is satisfactory for all purposes.

EXAMPLE II Another blend comprising 36% of the caustic washed gasoline, 54% of the doctor sweetened gasoline, 10% of styrene and 0.01% by weight of the inhibitor had a sulfur content of 0.003% after 14 days in storage, which again represents a considerable reduction as compared to the 0.0132% mercaptans obtained in the absence of unsaturated compound and inhibitor and as compared to the 0.0115 mercaptans obtained in the absence of the unsaturated compound.

EXAMPLE III To another sample of the blend of Example II but utilizing indene as the unsaturated compound, the sample after 14 days had a mercaptan content of 0.0021%.

Another sample of the same blend but omitting the inhibitor had a mercaptan content of 0.0047% after 14 days. It is thus seen that the inhibitor in conjunction with the unsaturated compound reduces the mercaptan content to less than half of that obtained by the unsaturated compound alone. As was shown in Example I, the addition of the inhibitor without the olefin did not reduce the mercaptan content to a satisfactory value.

EXAMPLE IV To another sample of the blend of Example II but utilizing 10% by volume of octene-l after the unsaturated compound and 0.01% by weight of the inhibitor, the blend had a mercaptan content of 0.0038% by weight after 14 days in storage.

EXAMPLE V In this example, cyclohexene was utilized as the unsaturated compounds. The gasoline was another sample of the blend of Example II containing 0.01% by weight From the above data, it is noted that the mercaptan content after 9 days without inhibitor or methylpentadiene was 0.0132%. With the inhibitor but without the methylpentadiene the mercaptan content was 0.0111%. However, with 0.01% of the inhibitor and 1% of methylpentadiene the mercaptan content was 0.004'7%, with 2% of methylpentadiene the mercaptan content was 0.0043% and with 5% methylpentadiene the mercaptan content was 0.0038%. Referring again to Example I, it will be noted that the addition of 10% by volume of methylpentadiene and 0.01% by weight of the inhibitor reduced the mercaptan content to 0.004%.

I claim as my invention:

1. A method of reducing the mercaptan content of a saturated petroleum hydrocarbon distillate containing an objectionable amount of mercaptans which comprises commingling therewith an olefinic hydrocarbon in an amount of from about 1% to about 10% by volume of said distillate and a phenylene diamine inhibitor in an amount of from about 0.0001% to about 0.1% by weight of said distillate, and reacting said hydrocarbon and inhibitor with the mercaptan content of the distillate in the presence of oxygen.

2. A method of reducing the mercaptan content of a saturated petroleum hydrocarbon distillate which comprises commingling therewith from about 1% to about 10% by volume of methylpentadiene and from about 0.0001% to about 0.1% by weight of N,N'-di-sec-butylp-phenylene diamine and reacting said compounds with the mercaptan content of the distillate in the presence of oxygen.

3. A method of reducing the mercaptan content of a saturated petroleum hydrocarbon distillate which comprises commingling therewith from about 1% to about 10% by volume of styrene and from about 0.0001% to about 0.1% by weight of N,N'-di-sec-buty1-p-phenylene diamine, and reacting said compounds with the mercaptan content of the distillate in the presence of oxygen.

4. A method of reducing the mercaptan content of a saturated petroleum hydrocarbon distillate which comprises commingling therewith from about 1% to about 10% by volume of an olefin and from about 0.0001% to about 0.1% by Weight of N,N'-di-sec-butyl-p-phenylene diamine, and reacting said compounds with the mercaptan content of the distillate in the presence of oxygen.

5. A method of reducing the mercaptancontent of a saturated petroleum hydrocarbondistillate which comprises commingling therewith from about 1% to about 10% by volume of a di-olefin and from about 0.000l% I 6. A method of reducing the mercaptan content of a This sample was acci-' saturated petroleum hydrocarbon distillate which comprises commingling therewith from about 1% to about 10% by volume of a cycloolefin and from about 0.0001 to about 0.1% by Weight of N,N-di-sec-butyl-p-phenylene diamine, and reacting said compounds with the mercaptan content of the distillate in the presence of oxygen.

7. A method of reducing the mercaptan content of a saturated petroleum hydrocarbon distillate which comprises commingling therewith from about 1% to about 10% by volume of indene and from about 0.0001% to about 0.1% by weight of N,N'-di-sec-butyl-p-pheny1ene diamine, and reacting said compounds with the mercaptan content of the distillate in the presence of oxygen.

8. A method of reducing the mercaptan content of a saturated gasoline containing an objectionable amount of mercaptans which comprises adding to said gasoline from about 1% to about 10% by volume of an olefinic hydrocarbon and from about 0.0001% to about 0.1% by weight of a phenylene diamine inhibitor, and reacting said hydrocarbon and inhibitor with the mercaptan content of the distillate in the presence of oxygen.

9. A method of reducing the mercaptan content of straight run gasoline which comprises adding to said gasoline from about 1% to about 10% by volume of methylpentadiene and from about 0.0001% to about 0.1% by weight of N,N-di-sec-butyl-p-phenylene diamine, and reacting said compounds with the mercaptan content of the distillate in the presence of oxygen.

10. The method of claim 1 further characterized in that said olefinic hydrocarbon is an aliphatic di-olefin.

11. The method of claim 1 further characterized in that said olefinic hydrocarbon, is methylpentadiene.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,402,863 Zuidema et a1 June 25, 1946 2,508,817 Devol et a1. May 23, 1950 

1. A METHOD OF REDUCING THE MERCAPTAN CONTENT OF A SATURATED PETROLEUM HYDROCARBON DISTILLATE CONTAINING AN OBJECTIONABLE AMOUNT OF MERCAPTANS WHICH COMPRISES COMMINGLING THEREWITH AN OLEFINIC HYDROCARBON IN AN AMOUNT OF FROM ABOUT 1% TO ABOUT 10% BY VOLUME OF SAID DISTILLATE AND A PHENYLENE DIAMINE INHIBITOR IN AN AMOUNT OF FROM ABOUT 0.0001% TO ABOUT 0.1% BY WEIGHT OF SAID DISTILLATE, AND REACTING SAID HYDROCARBON AND INHIBITOR WITH THE MERCAPTAN CONTENT OF THE DISTILLATE IN THE PRESENCE OF OXYGEN. 